Shrinkage Cracks In Concrete Slab

Shrinkage cracks in a slab photo above are unlikely to be of any structural concern but can be a source of water entry or radon entry in buildings and may form a tripping hazard.

Shrinkage cracks in concrete slab.

Similar uncontrolled or random cracks sometimes due to poor joint layout meander across the surface. Shrinkage cracking can be managed by the use of control joints placed in the slab. As the concrete slab dries after placement it shrinks. When concrete is mixed more water than is needed for hydration is mixed with the dry components such as sand cement and an aggregate.

This is the main cause of concrete shrinkage cracks on drying. Most of the water will eventually evaporate causing shrinkage of the concrete slab. See details at concrete shrinkage cracks. Some contractors cut or form a grid of small grooves in the slab to keep the shrinkage cracks in an orderly grid which looks better than random cracks but functions the same way.

This restraint creates tensile stresses in the concrete slab which in turn may produce drying shrinkage cracking. Plastic shrinkage concrete cracks when concrete is still in its plastic state before hardening it is full of water. Contraction joints or control joints when cracked are really just straight shrinkage cracks. While the concrete is shrinking many things such as reinforcement or the subgrade restrain the concrete.

Most of this excess water begins to exit the concrete during placement curing and causes the concrete to shrink. Shrinkage cracks in concrete occur due to change in moisture of concrete. While shrinkage in poured concrete walls or floor slabs is a normal property of curing concrete shrinkage cracks can be controlled or where they have occurred in some cases repairs are needed. Plastic shrinkage cracks are common in slabs.

These cracks are comparatively short cracks. Concrete and mortar are porous in their structure in the form of inter molecular space. When the evaporation of the moisture at the surface of concrete is more than the availability of the rising bleed to fill the surface moisture if this process happens before concrete attaining its tensile strength the volume change may cause cracks. In addition to reading about repairing concrete shrinkage cracks if crack repair is needed at all.